I've been implementing PSSM (http://http.developer.nvidia.com/GPUGems3/gpugems3_ch10.html) so far for cascaded shadow mapping. I've been reading abit about SDSM (http://visual-computing.intel-research.net/art/publications/sdsm/sampleDistributionShadowMaps_SIGGRAPH2010_notes.pdf) recently, and I'm not sure I understand the difference between them.
From what I gather, PSSM uses a logarithmic division of the splits with static near/far Z-bounds (such as the near/far view distance), while SDSM first transforms all visible objects into the cameras view space, finds the min/max Z and use it for the same split formula as PSSM (logarithmic).
What I find confusing though is that the PSSM article then in section 10-2 builds a crop matrix which takes the smallest of the frustrum AABB and the visible objects combined AABB... resulting in the same tight frustrum as SDSM does...? Isn't that the exact same thing?
Another thing not mentioned in the SDSM article is tightening the frustrums in x/y dimensions?